Brownfield, MO
07-06-06
Soybean aphid numbers low; but for how long?
by Jason Vance
South Dakota and Minnesota are seeing some heavy populations of soybean
aphids, but aphid numbers are very low throughout the rest of the Midwest.
Despite the extremely low number of aphids, Dr. Marlin Rice, a professor of
entomology at Iowa State University says it’s still important to scout for aphids.
“Over the past five years we have seen a lot of acres that need spraying in late
July, so even though populations are low now, it’s not something to ignore,” Rice
says.
At the same time, Rice says it’s not something to get overly excited about. It’s
easy to scout a field and at that time if you have a population averaging about
250 aphids per plant on 80 percent of the plants, that is a field that would benefit
from being sprayed.
As farmers scout for soybean aphids they need to be aware of other small
insects that may resemble aphids. Immature whiteflies, known as crawlers can
easily be mistaken for soybean aphids. Another look-a-like is an insect called
thrips.
“Farmers need to make certain of the identity of soybean aphids and make sure
they are spraying the right insects,” Rice says. “They certainly shouldn’t waste
money spraying an insect that’s not going to cause any damage.”
Neither whiteflies nor thrips cause damage to soybeans, so Rice says producers
should ignore them while scouting.
Rice says that soybean aphids are an unpredictable insect in that it’s unknown
what is going to happen between now and early August.
“We know we are going to have aphids,” Rice says. “We just don’t know how
many and where problems are going to occur.” That’s why he encourages
scouting so producers catch aphids early.